Last week, the U.S. Bureau of Land Management sold 15 leases for about 18,000 acres in California’s Monterey Shale, which stretches 200 miles south from San Francisco. The U.S. Energy Information Administration estimates the shale formation could hold 15.4 billion barrels of oil, which would be double the combined reserves of the Bakken formation in North Dakota and the Eagle Ford shale of South Texas, Bloomberg News reports.

Los Angeles-based Occidental Petroleum snapped up most of the leases sold at the auction, and California lawmakers have drafted new rules to deal with a boom in hydraulic fracturing.